hrough protein and DNA sequence analysis, much information on he primary structure of proteins has accumulated over the past everal years. We have used this information to prepare ntibodies reactive with defined portions of proteins. This is one by synthesizing 10-30 residue peptides that correspond to ections of the sequence of the protein. After coupling to a rotein carrier, antisera to the peptides are prepared. In the ase of transplantation and other lymphocyte antigens, these ntibodies are used to define sites of cellular recognition and erological specificities. In the case of viral antigens, the ntisera have been used as specific probes to detect the xpression of endogenous retroviral DNA found in human cells nd will be used to attempt to enhance the immune response to a ew flu vaccine. In some cases, the rabbit anti-peptide sera ail to react with the native protein and, therefore, nti-peptide hybridomas are being made and the hybrid clones creened for reactivity with native protein. Anti-peptide sera gainst the complementarity determining regions (CDR) of an mmunoglobulin have been prepared and will be tested for their bility to kill the parent myeloma. Finally, peptides have een synthesized to be used to define the epitopes recognized y monoclonal antibodies to the p. falciparum sporozoite and he cytochrome C molecule.